One approach to producing multiple voltage outputs from a single power supply cascades a series of voltage output circuits together. The overall efficiency of the power supply decreases with the addition of each cascaded voltage output circuit. Another approach to producing multiple voltage outputs from a single power supply is to use a power supply having flyback topology. In a power supply having a flyback topology, generally only one voltage output can be regulated to provide the desired nominal output voltage.
One technique for regulating additional output voltages of a power supply having a flyback topology makes use of a linear regulator. Typically, the linear regulator compares the output voltage to a reference voltage that is indicative of the desired nominal output voltage and uses the difference between the output voltage and the reference voltage to change the resistance of a variable resistor, which changes the output voltage. The variable resistor is typically implemented using a transistor, which when used this way, dissipates a large amount of heat. The loss of heat typically reduces the efficiency of the power supply considerably.